The temperature- and frequency-dependent ac conductivity of nanoporous metal-oxide semiconductors commonly
used in technologies for solar photoconversion is analyzed by using a model based on fluctuation-induced tunneling
conduction (FITC). The model takes into account voltage fluctuations of potential barriers that limit electron
transport at nanoparticle contact junctions. In contrast to previous models, quantitative agreement over the
entire temperature range studied is found by using the FITC model based on a single set of parameters. Guidelines
for the design of new materials for dye-sensitized solar cells (DSSCs) and solar photocatalysis are discussed.